<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>mydemo</title>
	<style type="text/css">
		#outer {width:100%;margin:10px auto;text-align:center;font:12px/1.5;}
		#sum {margin:10px;display:inline;color:green;}
		#first,#second {margin:0 10px;width:50px;}
	}
	</style>
	<script type="text/javascript">
		/* 获取两个输入框的值和sum值 */
		window.onload = function() {
			var oInput = document.getElementsByTagName("input");
			for(var i=0;i<2;i++) {
				oInput[i].onkeyup = function() {
					this.value = this.value.replace(/[^\d|","]/,"");
				}
				oInput[2].onclick = function() {
					var f = document.getElementById("first").value;
					var s = document.getElementById("second").value;
					var oSum = document.getElementById("sum");
					var sum = 0
					console.log(oSum);
					sum += parseInt(f) + parseInt(s);
					oSum.innerHTML = sum;
				}
			}				
		}		
	</script>
</head>
<body>
	<div id="outer">
		<input type="text" id="first">+<input type="text" id="second">=<div id="sum">?</div><input type="button" value="求和">
	</div>
</body>
</html>